A 6-year-old boy has recurrent abscesses caused by Staphylococcus aureus and Aspergillus, lymphadenitis, and absent pus despite marked neutrophilia. The neutrophil oxidative burst test shows no chemiluminescence after phorbol ester stimulation. Which enzyme complex is defective?

• A Myeloperoxidase
• B Inducible nitric oxide synthase
• C NADPH oxidase ✓
• D Cytochrome b5 reductase

Explanation

Chronic granulomatous disease results from mutations in components of the phagocyte NADPH oxidase (NOX2 complex), which transfers electrons from NADPH to oxygen to generate superoxide inside the phagosome. Without superoxide and its downstream reactive species, catalase-positive organisms such as S aureus and Aspergillus survive intracellularly, producing granulomas and abscesses with absent pus. Myeloperoxidase deficiency exists but leaves the superoxide burst intact, so the stimulated chemiluminescence would be preserved.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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